Large amount of various toxic, corrosive, and combustible gases are generally used in the semiconductor manufacturing processes.
For instance, large amount of silane, dichlorosilane, ammonia, nitrogen oxide, arsine, phosphine, divorine, borone, trichloride, etc. are used in a chemical vapor deposition (CVD) process. Only small amount of these are consumed during the manufacturing process, waste gases (perfluoro-compounds; PFCs) discharged therefrom contain highly concentrated harmful substances such as CF4, SF6, NF3, etc.
In addition, various kinds of harmful waste gases are produced even in different semiconductor manufacturing processes such as low pressure CVD, plasma enhanced CVD, plasma etching, epitaxial deposition, etc.
The Environmental Law currently requires that the harmful substances in the waste gas should be removed prior to discharging the waste gas into the air.
Therefore, various techniques have heretofore been studied and practiced for the treatment of waste gases discharged from the semiconductor manufacturing processes. However, none of these waste gas treatment apparatuses developed heretofore have proved unsatisfactory in their capacity and their effectiveness, and many defects have been found therein.
Waste gas treatment methods that have been used conventionally may be largely classified into those of a wet-type, and a dry-type, but potential problems including manufacturing cost or effectiveness in each apparatus have been existed.
In a wet-type waste gas treatment apparatus, water is scattered in the waste gas, and reaction particles of harmful components, which react with water, are collected. The apparatus has excellent capabilities for treating harmful components, but there are disadvantages that a drain can be damaged by scattering materials during treatment process, particles of water droplets containing harmful components are scattered toward a ventilating passage, thereby eroding a ventilating duct, and therefore various kinds of water soluble pollutants should be inevitably removed prior to discarding the used water.